With the development of a wireless communication technology, a wireless communication system raises higher requirements on high sensitivity transmitting, high sensitivity receiving, and high quality of voice communication. For a filter in a base station, it is necessary to achieve less insertion loss and better suppression performance. In addition, with regard to the filter, a strong desire for reducing the size of the filter. A TM mode dielectric filter may exactly satisfy the above demand. Compared with a common metal coaxial filter of the same volume, it may have about a 30% increase of a quality factor value (Q value). The TM mode dielectric filter may be made up of several TM mode dielectric resonators cascaded in a particular way.
A typical TM mode dielectric resonator includes a dielectric resonant column and a metal resonant cavity. Also, top and bottom end surfaces of the dielectric resonant column need to closely fit in with top and bottom end surfaces of the metal resonant cavity, so that a current can smoothly flow through a contact surface between the dielectric resonant column and the metal resonant cavity, therefore forming a good current loop. In addition, because there is a strong current on the contact surface between the top and bottom surfaces of the dielectric resonant column and the metal resonant cavity of the TM mode resonator, good contact between the two contact surfaces is essential and important. Therefore, in a design process of the TM mode dielectric resonator, it is necessary to guarantee good contact between the contact surfaces and good structure reliability with respect to a structure and/or process, so as to achieve a good Q value and passive intermodulation (PIM) value of the TM mode resonator and thus provide stable performance.
The conventional dielectric resonator cannot achieve good contact between the contact surfaces, or its assembly is complex, or a welding process is required to cause the top and bottom end surfaces of the dielectric resonant column to contact the top and bottom end surfaces of the metal cavity. Because the welding cost is high, and the stability of the welding process seriously affects the product yield, it is necessary to strictly control the welding process. In addition, the existence of a welding point may lead to unstable performance when the dielectric resonant column vibrates.